The Maryland Senate voted Wednesday to make Maryland the 18th state to abolish the death penalty, putting Gov. Martin O'Malley one step closer to a significant legislative victory.

The 27-20 vote sent the bill to the House of Delegates, where repeal supporters believe they have enough backing to send the legislation to the governor.

Two Republicans — Sens. Edward R. Reilly of Anne Arundel County and Allan H. Kittleman of Howard County — joined 25 Democrats in supporting repeal. Ten Democrats and 10 Republicans opposed the legislation.

The Senate has been viewed by repeal proponents as a tougher challenge than the House. In 2009, the last year O'Malley pushed to end capital punishment, the effort ended in a compromise that narrowed the circumstances under which the death penalty could be sought.

This year, the NAACP decided to make repeal in Maryland a priority and urged O'Malley to include it in his legislative agenda. Senate President Thomas V. Mike Miller, despite his personal support for capital punishment, promised to allow an up-or-down vote in his chamber if O'Malley could show he had the votes to pass the bill.

After the vote, Miller gave O'Malley — along with the NAACP, the Catholic Church and other religious groups — credit for the bill's passage.

"He chose to push it hard. I think he'll meet with success in the House of Delegates," said Miller, a Calvert County Democrat. But he also predicted a close vote if the bill is petitioned to a referendum in 2014, as he expects it to be.

Miller said death penalty opponents are right when they say the system is "broken," but said it should be corrected instead of abolished. "Justice should be sure and justice should be swift," he said.

A breakthrough for death penalty opponents came when Sen. Robert A. Zirkin, a Baltimore County Democrat, reversed his previous opposition to repeal and provided the sixth vote needed to approve the bill in the Judicial Proceedings Committee and send it to the Senate floor. There, opponents of the legislation tried repeatedly but failed to win approval of amendments creating various exceptions to full repeal.

Zirkin took to the floor Wednesday to say he had no sympathy for killers such as the five men currently on death row in Maryland for murders committed as far back as 1983.

"There are horrible monsters," Zirkin said. "If you were always 100 percent sure, I think we would all agree they don't deserve to live."

But Zirkin said he couldn't accept even the remote possibility that Maryland could execute somebody who was innocent.

That was the argument that ultimately swayed Kittleman, who said he was still wrestling with the decision as floor debate got under way last week.

"DNA evidence isn't always conclusive, and we've made that the Holy Grail," Kittleman said. He said he was swayed to believe that DNA evidence "indicates presence, not guilt."

"I don't think I'm protecting the criminals. I think I'm protecting the innocent," Kittleman said.

As if to underscore that point, Kirk Bloodsworth — exonerated by DNA testing after being sentenced to death in Baltimore County for the murder of a young girl — was in the Senate gallery Wednesday to witness the vote.

Supporters of capital punishment countered that since 2009, Maryland has had one of the most restrictive death penalty laws in the country. Prosecutors are able to seek the death penalty only when they have biological evidence, a videotape of the crime or a video-recorded confession by the killer.

Senate Minority Leader E. J. Pipkin, an Eastern Shore Republican, said a case such as Bloodsworth's couldn't happen today. Pipkin said he was tired of hearing repeal supporters' constant repetition of his name. Sen. Jamie Raskin, the floor leader for the pro-repeal forces, said that while some senators may be suffering from "Kirk Bloodsworth fatigue," he was not.

After the vote Bloodsworth said he was "tickled pink" at the outcome, adding that an unjust conviction is something that "can happen to anybody."

The burly ex-waterman caught Sen. Brian E. Frosh, a death penalty foe who chairs the Judicial Proceedings Committee, in a congratulatory bear hug.